It is known in U.S. Pat. No. 4,527,630 to provide a hydraulically actuated well safety valve with first and second flow sealing valves. The first sealing valve is positioned to shut off fluid flow from a fluid control passageway to the piston and cylinder assembly when the safety valve is in the open position and the second sealing valve is positioned to shut off fluid flow from the cylinder to the flow control passageway when the safety valve is in the closed position. In such a safety valve biasing fluid in the safety valve advantageously acts against the piston and cylinder assembly in a direction to move the safety valve to the closed position. However, contaminants in the biasing fluid collect on the second flow sealing valve element and valve seat and prevent the second valve from providing a gas tight seal. Therefore, gas may escape from the biasing fluid which comprises well production fluid. Such gases, which are flammable, may flow through the piston and cylinder assembly and up the fluid control passageway to the well surface to affect the fluid control operation of the safety valve and to create a hazardous surface condition.
The present invention is directed to the provision of a well subsurface safety valve having a hydraulic valve actuating means including flow sealing valves which are positioned out of direct contamination with the biasing fluid for reducing the possibility of gas escaping to the fluid control passageway.